There are many types of vacuum pumps in various industries including: chemical, pharmaceutical, tobacco, coating, steel refinery, degassing, electrical, packaging, power generation, semiconductor, and many more. Specific examples include: liquid ring pumps, kinetic pumps, vane pumps, rotary piston pumps, reciprocating pumps, screw pumps, claw pumps, scroll pumps, multistage roots pumps, pre-inlet air cool roots pumps, and roots pump. However, among these pumps, the ordinary roots pump cannot discharge directly to the atmosphere. It must have one of the aforementioned pumps as its backing pump.
Among the pumps mentioned above, depending on the presence of water or other liquid involved directly with the process gas in the pump operation, there are basically two types of pumps: dry vacuum pumps and water/liquid vacuum pumps. As environmental protection becomes a larger concern for society, dry vacuum pumps are increasingly demanded by all industries. Reciprocating pumps, screw pumps, scroll pumps, vane pumps, multi-stage roots pumps, claw pumps and pre-inlet air cooling roots pumps can all be transformed into dry vacuum pumps.
Pumps that do not use water and a vacuum generation media are dry vacuum pumps. Since dry pumps do not generate water pollution, the vacuum industry is moving towards dry technology. However, despite the many kinds of dry vacuum pumps available, each one has its own limitations. None of the dry vacuum pumps have a high suction capacity (bigger than 3000 m3/h) or sufficient vacuum level (10 Pa or better), that is tolerant to corrosion, sticky materials and dust at the same time. This limits the application of dry vacuum pumps in industrial applications. Therefore, in terms of overall suction capacity, powder and corrosion handling in all industrial applications, the dry vacuum process is still used far less than other pumps that involve water or oil. This causes those industries to remain major sources of pollution to the world.
The roots vacuum pump is a very popular dry vacuum pump. It has the biggest suction capacity in general among all pumps, a very high vacuum level up to 0.01 Pa, and is very resistant to corrosion and dust given the same application conditions. However, limited by its structure, unlike the other pumps mentioned above, this type of pump cannot discharge the gas directly to the atmosphere unless a backing pump exists. Although the pre-inlet air cooling roots pump is one kind of “roots pump” which can discharge gas directly to the atmosphere, it needs the discharged air to be cooled and then reintroduced back to the pump body to cool the pump to prevent the pump from an overheat failure. Therefore, it is inefficient and can only achieve a very rough vacuum to only 10-15 kPa level with excess noise and a high energy consumption, making it non-conducive for most processes.
The multi-stage roots pump is a decent dry vacuum pump. However, it shares two coaxial axles across all vacuum chambers and it has a limited flow path, limited number of stages and limited suction capacity, making it too narrow, small, and crowded, with too many dead corners in the air flow path. In addition to all of these characteristics, with the pump structure, the heat will kill the preset clearance among all chambers when the pump works hard. Therefore, a large-scale multi-stage roots pump cannot be made.
To avoid the limitation of the multi-stage roots pump, a separated multistage roots pump Japanese invention has been developed. It is a group of independent roots pumps combined with heat exchangers to form a type of multistage roots pump. However, it is not a pump unit, but a normal multistage pump set system. The business named in this application in the last several years tried to sell such a concept to customers, but in vain. Almost all customers want to have a single pump, not a set of pumps that need to be installed together on-site. In addition, this multistage group roots pump is also limited to a 0.1 mm clearance between the blade and pump case and a different rpm, but the size of each chamber remains the same. Such a pump is designed for the semiconductor industry, not for chemical, metallurgy, edible oil, power industry, or others.
The aim of this invention is to make a dry vacuum pump that can run by itself without a backing pump, and has as big as a 10,000 m3/h suction capacity, as high as a 1 to 10,000 Pa vacuum, and is still as resistant to corrosion and dust as the best roots pump can do among all dry pumps available today. It is made by modularized components but assembled into one single unit solid pump ready for use.